The present invention relates to a buckle for a vehicle safety restraint seat belt.
In modern vehicles there is often a requirement to sense whether a seat belt is employed and if not to provide warning lights and/or audible signals to encourage the vehicle occupant to use the seat belt. Deployment of the belt is usually detected by a switch such as a reed switch in the buckle body which is sensitive to the proximity of a tongue inserted in the receiving passage of the buckle head.
There is a further requirement in modern safety restraint systems to sense the information about seat belt deployment, and vehicle occupancy in microcomputer controlled systems. For example it may be desirable to disable an airbag or a seat belt pretensioner if the belt is not deployed, or the timing of airbag deployment may be different depending upon whether the belt is worn. Certain crash conditions may also be taken into account.
A disadvantage of known systems of detecting the deployment of a seat belt is that they can not distinguish between the seat belt tongue itself and other foreign bodies spuriously inserted (or having fallen) into the buckle opening. Thus a false indication of usage may occur. In particular they cannot distinguish between tongues and will provide wrong information if for example, the passenger""s tongue is inserted in the driver""s buckle.
The present invention aims to provide an improved buckle from which more accurate and reliable information on seat belt usage can be obtained.
According to one aspect of the present invention there is provided a safety restraint seat belt arrangement comprising a buckle head, and a buckle tongue, the buckle head comprising a passageway for receiving the tongue, and releasable means for locking the tongue in the passageway, and wherein a tag is provided in the tongue and a detector, sensitive to the tag is provided in the buckle head in proximity to the tongue passageway.
The tag may be a coded magnetic strip, or a microchip embodying a code, encapsulated in the material of the tongue (which is usually metal but may be any strong material). The detector is chosen to be suitable to read the tag. The code may be arranged to uniquely identify each tongue in a particular vehicle or be programmable by the sensor at the vehicle manufacturer. Each detector in the buckle heads may be programmed to recognise its corresponding correct tongue and warning signals may be provided if the wrong tongue, or a different object is inserted into a particular buckle. The tags may be encapsulated to prevent damage during normal buckle usage.
Alternatively the tags may be optically coded, with light sensitive detectors in the buckle heads. For example a form of bar code and bar code reader would be a relatively cheap way of implementing the present invention.
Such a system can also be arranged so that substandard spare parts such as replacement tongues are rejected since the detector in the buckle will only recognise a tongue with the correctly coded tag installed.
In one embodiment, a specially coded tag would be used in tongues for child or baby seats and the sensor signals used to disable an associated airbag as a consequence, since airbags can be dangerous to infants, particularly when a rear facing baby seat is installed.
In another aspect the invention also provides a buckle tongue for use in the buckle of the first aspect, and which comprises an identifying coded tag.
According to a preferred embodiment the buckle further comprises a lock out device which prevents locking of the tongue in the buckle head unless the correct tongue is presented in the passageway. For example, the lock out device may comprise a sliding plate interposed between the movable buckle locking member and the tongue, to block engagement of the locking member with the tongue, (usually with a recess in the tongue).